Table 1 Baseline and stimulation characteristics of cleavage-stage and blastocyst-stage embryo transferred cohorts
| Â | Cleavage-Stage Embryo Transferred | Blastocyst-Stage Embryo Transferred | P-value |
|---|---|---|---|
N = 2342 | N = 2129 | ||
Progesterone on day of trigger (ng/ml) | 1.00 (0.69–1.37) | 1.17 (0.84–1.53) |  < 0.001 |
Year of treatment, n (%) |  |  |  < 0.001 |
 2018 | 272 (11.61%) | 90 (4.23%) |  |
 2019 | 677 (28.91%) | 563 (26.44%) |  |
 2020 | 786 (33.56%) | 803 (37.72%) |  |
 2021 | 607 (25.92%) | 673 (31.61%) |  |
Female age (years) | 33.00 (30.00–37.00) | 32.00 (30.00–36.00) |  < 0.001 |
Female age (years), n (%) |  |  |  < 0.001 |
 < 30 | 945 (40.35%) | 977 (45.89%) |  |
 30–34 | 461 (19.68%) | 464 (21.79%) |  |
 35–37 | 420 (17.93%) | 374 (17.57%) |  |
 38–42 | 516 (22.03%) | 314 (14.75%) |  |
Male age (years) | 34.00 (31.00–38.00) | 33.00 (30.00–37.00) |  < 0.001 |
BMI (kg/m2) | 22.32 (20.31–24.84) | 22.38 (20.40–24.61) | 0.495 |
BMI (kg/m2), n (%) | Â | Â | 0.813 |
 < 20 | 1627 (69.47%) | 1503 (70.60%) |  |
 20–24.99 | 164 (7.00%) | 156 (7.33%) |  |
 25–29.99 | 462 (19.73%) | 391 (18.37%) |  |
 ≥ 30 | 86 (3.67%) | 77 (3.62%) |  |
 Missing | 3 (0.13%) | 2 (0.09%) |  |
Smoking, n (%) | 651 (27.80%) | 611 (28.70%) | 0.503 |
Infertility duration (years) | 3.00 (2.00–5.00) | 3.00 (2.00–5.00) | 0.006 |
Gravidity,n (%) | Â | Â | 0.202 |
 0 | 922 (39.47%) | 889 (41.99%) |  |
 1 | 628 (26.88%) | 533 (25.18%) |  |
 ≥ 2 | 786 (33.65%) | 695 (32.83%) |  |
Parity,n (%) | Â | Â | 0.119 |
 0 | 1694 (72.67%) | 1574 (74.63%) |  |
 1 | 559 (23.98%) | 454 (21.53%) |  |
 ≥ 2 | 78 (3.35%) | 81 (3.84%) |  |
Cause of infertility, n (%) |  |  |  < 0.001 |
 Male factor | 429 (18.32%) | 343 (16.11%) |  |
 Tubal factor | 1257 (53.67%) | 1314 (61.72%) |  |
 Ovulatory disorder | 328 (14.01%) | 229 (10.76%) |  |
 Endometriosis | 146 (6.23%) | 69 (3.24%) |  |
 Unexplained | 182 (7.77%) | 174 (8.17%) |  |
Basal FSH (mIU/mL) | 7.79 (6.34–9.85) | 7.29 (6.04–9.01) |  < 0.001 |
Antral follicle count | 6.00 (5.00–9.00) | 8.00 (6.00–11.00) |  < 0.001 |
Rank of cycle | 1.00 (1.00–2.00) | 1.00 (1.00–1.00) |  < 0.001 |
Fertilization methods, n (%) |  |  |  < 0.001 |
 IVF | 1714 (73.19%) | 1762 (82.76%) |  |
 ICSI | 621 (26.52%) | 359 (16.86%) |  |
 IVF + ICSI | 7 (0.30%) | 8 (0.38%) |  |
Gonadotrophins (IU) | 2400.00 (2025.00–3000.00) | 2400.00 (1875.00–2925.00) |  < 0.001 |
Gonadotrophin type, n (%) |  |  |  < 0.001 |
 FSH | 484 (20.67%) | 544 (25.55%) |  |
 FSH + LH | 1858 (79.33%) | 1585 (74.45%) |  |
LH on day of trigger (mIU/mL) | 2.28 (1.42–3.72) | 2.11 (1.27–3.36) |  < 0.001 |
Estradiol on day of trigger (pg/ml) | 1557.60 (991.00–2565.97) | 2338.48 (1541.88–3540.00) |  < 0.001 |
Oocytes retrieved | 5.00 (3.00–8.00) | 8.00 (5.00–10.00) |  < 0.001 |
Two-pronuclei | 3.00 (2.00–4.00) | 5.00 (4.00–7.00) |  < 0.001 |
Viable embryos | 2.00 (1.00–3.00) | 5.00 (4.00–7.00) |  < 0.001 |
Number of embryos transferred | 1.00 (1.00–2.00) | 1.00 (1.00–1.00) |  < 0.001 |
 1, n (%) | 1218 (52.01%) | 1841 (86.47%) |  < 0.001 |
 2, n (%) | 1117 (47.69%) | 288 (13.53%) |  |
 3, n (%) | 7 (0.30%) | 0 (0.00%) |  |